179 research outputs found
Deformation Energy Minima at Finite Mass Asymmetry
A very general saddle point nuclear shape may be found as a solution of an
integro-differential equation without giving apriori any shape parametrization.
By introducing phenomenological shell corrections one obtains minima of
deformation energy for binary fission of parent nuclei at a finite (non-zero)
mass asymmetry. Results are presented for reflection asymmetric saddle point
shapes of thorium and uranium even-mass isotopes with A=226-238 and A=230-238
respectively.Comment: 5 pages, 2 Postscript figures, REVTeX, Version 4.
Encephalocele – A Single Institution African Experience
Objective: This study seeks to find out the presentation, management and complications of encephaloceles in an African setting.Design: a retrospective study reviewing the age and sex of the patients, type and contents of encephaloceles, associated anomalies, preoperative evaluation and investigations, surgical approaches, intra- and post-operative complications as well as follow-up outcomes.Setting: Bethany Crippled Children’s centre and Bethanykids at Kijabe Hospital (BKKH), between January 1998 and August 2006.Patients: Of the 53 patients seen, 23 were males and 30 females. The median age at presentation was four months.Results: The follow-up period extended to eight years. Twenty nine patients had occipital encephaloceles, and 39 were operated using the direct external approach. Cererobrospinal fluid leak was the most common post-operative complication. Recurrence occurred in four patients and death in six.Conclusions: Most of the encephalocele patients managed at BKKH had good outcomes and proceeded to live normal or near-normal lives. Our study confirms that even in resource-constrained areas, children with encephaloceles can be successfully managed with acceptable outcomes
Topological defects in spinor condensates
We investigate the structure of topological defects in the ground states of
spinor Bose-Einstein condensates with spin F=1 or F=2. The type and number of
defects are determined by calculating the first and second homotopy groups of
the order-parameter space. The order-parameter space is identified with a set
of degenerate ground state spinors. Because the structure of the ground state
depends on whether or not there is an external magnetic field applied to the
system, defects are sensitive to the magnetic field. We study both cases and
find that the defects in zero and non-zero field are different.Comment: 10 pages, 1 figure. Published versio
Cosmology in a String-Dominated Universe
The string-dominated universe locally resembles an open universe, and fits
dynamical measures of power spectra, cluster abundances, redshift distortions,
lensing constraints, luminosity and angular diameter distance relations and
microwave background observations. We show examples of networks which might
give rise to recent string-domination without requiring any fine-tuned
parameters. We discuss how future observations can distinguish this model from
other cosmologies.Comment: 17 pages including 4 figures, of which one is in colo
Fine structure of alpha decay in odd nuclei
Using an alpha decay level scheme, an explanation for the fine structure in
odd nuclei is evidenced by taking into account the radial and rotational
couplings between the unpaired nucleon and the core of the decaying system. It
is stated that the experimental behavior of the alpha decay fine structure
phenomenon is directed by the dynamical characteristics of the system.Comment: 8 pages, 3 figures, REVTex, submitted to Physical Review
Congenital anomalies in low- and middle-income countries: the unborn child of global surgery.
Surgically correctable congenital anomalies cause a substantial burden of global morbidity and mortality. These anomalies disproportionately affect children in low- and middle-income countries (LMICs) due to sociocultural, economic, and structural factors that limit the accessibility and quality of pediatric surgery. While data from LMICs are sparse, available evidence suggests that the true human and financial cost of congenital anomalies is grossly underestimated and that pediatric surgery is a cost-effective intervention with the potential to avert significant premature mortality and lifelong disability
Microscopic description of cluster radioactivity in actinide nuclei
Cluster radioactivity is the emission of a fragment heavier than an α particle and lighter than mass 50. The range of clusters observed in experiments goes from 14C to 32Si while the heavy mass residue is always a nucleus in the neighborhood of the doubly-magic 208Pb nucleus. Cluster radioactivity is described in this paper as very asymmetric nuclear fission. A new fission valley leading to a decay with large fragment mass asymmetry matching the cluster radioactivity products is found. The mass octupole moment is found to be more convenient than the standard quadrupole moment as the parameter driving the system to fission. The mean-field Hartree-Fock-Bogoliubov theory with the phenomenological Gogny interaction has been used to compute the cluster emission properties of a wide range of even-even actinide nuclei from 222Ra to 242Cm, where emission of the clusters has been experimentally observed. Computed half-lives for cluster emission are compared with experimental results. The noticeable agreement obtained between the predicted properties of cluster emission (namely, cluster masses and emission half-lives) and the measured data confirms the validity of the proposed methodology in the analysis of the phenomenon of cluster radioactivity. A continuous fission path through the scission point has been described using the neck parameter constraintThe work of LMR was supported by Ministerio de Ciencia e Innovacion (Spain) Grants No. FPA2009-08958 and No. FIS2009-07277, as well as by Consolider-Ingenio 2010 Programs CPAN CSD2007-00042 and MULTIDARK CSD2009- 00064. The work of MW was supported by Ministerstwo Nauki i Szkolnictwa Wyzszego (Poland) under Grant No. N N202 23113
Emission of intermediate mass fragments from hot Ba formed in low-energy Ni+Ni reaction
The complex fragments (or intermediate mass fragments) observed in the
low-energy Ni+NiBa reaction, are studied within
the dynamical cluster decay model for s-wave with the use of the
temperature-dependent liquid drop, Coulomb and proximity energies. The
important result is that, due to the temperature effects in liquid drop energy,
the explicit preference for -like fragments is washed out, though the
C (or the complementary Sn) decay is still predicted to be one
of the most probable -nucleus decay for this reaction. The production
rates for non- like intermediate mass fragments (IMFs) are now higher
and the light particle production is shown to accompany the IMFs at all
incident energies, without involving any statistical evaporation process in the
model. The comparisons between the experimental data and the (s-wave)
calculations for IMFs production cross sections are rather satisfactory and the
contributions from other -waves need to be added for a further
improvement of these comparisons and for calculations of the total kinetic
energies of fragments.Comment: 22 pages, 15 figure
Adiabatic description of nonspherical quantum dot models
Within the effective mass approximation an adiabatic description of
spheroidal and dumbbell quantum dot models in the regime of strong dimensional
quantization is presented using the expansion of the wave function in
appropriate sets of single-parameter basis functions. The comparison is given
and the peculiarities are considered for spectral and optical characteristics
of the models with axially symmetric confining potentials depending on their
geometric size making use of the total sets of exact and adiabatic quantum
numbers in appropriate analytic approximations
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